Lusitropy
Encyclopedia
Lusitropy is a term used to describe myocardial relaxation. The increase in calcium
uptake by cardiomyocytes leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.
) via a cAMP-dependent pathway.
1) Calcium overload - too much intracellular calcium
2) Rate of efflux of calcium through pumps - if calcium is not removed from the cell quickly enough
3) Impaired sarcoendoplasmic reticulum calcium ATPase (SERCA
)- this channel in the myocyte pumps calcium from the cytoplasm of the cell into the endoplasmic reticulum.
4) TN-C binding affinity - TN-C (troponin C
) is a protein that affects the myosin-actin fibers of the heart. When calcium binds, it triggers contraction of the heart. If calcium binds too easily, relaxation will become more difficult.
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
uptake by cardiomyocytes leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.
Positive
Increased catecholamine levels promote positive lusitropy, enabling the heart to relax more rapidly. This effect is mediated by the phosphorylation of (phospholambanPhospholamban
Phospholamban, also known as PLN, is a protein that in humans is encoded by the PLN gene. Phospholamban is a 52-amino acid integral membrane protein that regulates the Ca2+ pump in cardiac muscle and skeletal muscle cells.- Function :...
) via a cAMP-dependent pathway.
Negative
Relaxation of the heart is negatively impacted by the following factors:1) Calcium overload - too much intracellular calcium
2) Rate of efflux of calcium through pumps - if calcium is not removed from the cell quickly enough
3) Impaired sarcoendoplasmic reticulum calcium ATPase (SERCA
SERCA
SERCA, or sarco/endoplasmic reticulum Ca2+-ATPase, or SR Ca2+-ATPase, is a calcium ATPase-type P-ATPase.-Function:SERCA resides in the sarcoplasmic reticulum within muscle cells...
)- this channel in the myocyte pumps calcium from the cytoplasm of the cell into the endoplasmic reticulum.
4) TN-C binding affinity - TN-C (troponin C
Troponin C
Troponin C is a part of the troponin complex. It contains four calcium-binding EF hands. It is a component of thin filaments . It contains an N lobe and a C lobe. The C lobe serves a structural purpose and binds to the N domain of TnI. The C lobe can bind either Ca2+ or Mg2+...
) is a protein that affects the myosin-actin fibers of the heart. When calcium binds, it triggers contraction of the heart. If calcium binds too easily, relaxation will become more difficult.